poky/meta/lib/oe/path.py
Richard Purdie 61823f6194 path.py: Deal with race issue
The change to use copyhardlinktree in some of the sstate code instead of
copytree exposed a race condition. This is due to cp failing if it finds
a directory doesn't exist yet some other process creates it while cp was
trying to create it itself. tar doesn't error in this case.

To fix this we need to create the directory structure with tar, then
use cp to hardlink the files. Messy but probably worth doing.

I also took the opportunity to remove src_bak since the code is neater
without it.

(From OE-Core rev: 2f954a9a6932f1e6c564e7e7aacaac628a75eed7)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
2013-05-03 16:19:19 +01:00

262 lines
8.6 KiB
Python

import errno
import glob
import shutil
import subprocess
import os.path
def join(*paths):
"""Like os.path.join but doesn't treat absolute RHS specially"""
return os.path.normpath("/".join(paths))
def relative(src, dest):
""" Return a relative path from src to dest.
>>> relative("/usr/bin", "/tmp/foo/bar")
../../tmp/foo/bar
>>> relative("/usr/bin", "/usr/lib")
../lib
>>> relative("/tmp", "/tmp/foo/bar")
foo/bar
"""
if hasattr(os.path, "relpath"):
return os.path.relpath(dest, src)
else:
destlist = os.path.normpath(dest).split(os.path.sep)
srclist = os.path.normpath(src).split(os.path.sep)
# Find common section of the path
common = os.path.commonprefix([destlist, srclist])
commonlen = len(common)
# Climb back to the point where they differentiate
relpath = [ os.path.pardir ] * (len(srclist) - commonlen)
if commonlen < len(destlist):
# Add remaining portion
relpath += destlist[commonlen:]
return os.path.sep.join(relpath)
def make_relative_symlink(path):
""" Convert an absolute symlink to a relative one """
if not os.path.islink(path):
return
link = os.readlink(path)
if not os.path.isabs(link):
return
# find the common ancestor directory
ancestor = path
depth = 0
while ancestor and not link.startswith(ancestor):
ancestor = ancestor.rpartition('/')[0]
depth += 1
if not ancestor:
print "make_relative_symlink() Error: unable to find the common ancestor of %s and its target" % path
return
base = link.partition(ancestor)[2].strip('/')
while depth > 1:
base = "../" + base
depth -= 1
os.remove(path)
os.symlink(base, path)
def format_display(path, metadata):
""" Prepare a path for display to the user. """
rel = relative(metadata.getVar("TOPDIR", True), path)
if len(rel) > len(path):
return path
else:
return rel
def copytree(src, dst):
# We could use something like shutil.copytree here but it turns out to
# to be slow. It takes twice as long copying to an empty directory.
# If dst already has contents performance can be 15 time slower
# This way we also preserve hardlinks between files in the tree.
bb.utils.mkdirhier(dst)
cmd = 'tar -cf - -C %s -ps . | tar -xf - -C %s' % (src, dst)
check_output(cmd, shell=True, stderr=subprocess.STDOUT)
def copyhardlinktree(src, dst):
""" Make the hard link when possible, otherwise copy. """
bb.utils.mkdirhier(dst)
if os.path.isdir(src) and not len(os.listdir(src)):
return
if (os.stat(src).st_dev == os.stat(dst).st_dev):
# Need to copy directories only with tar first since cp will error if two
# writers try and create a directory at the same time
cmd = 'cd %s; find . -type d -print | tar -cf - -C %s -ps --files-from - | tar -xf - -C %s' % (src, src, dst)
check_output(cmd, shell=True, stderr=subprocess.STDOUT)
if os.path.isdir(src):
src = src + "/*"
cmd = 'cp -afl %s %s' % (src, dst)
check_output(cmd, shell=True, stderr=subprocess.STDOUT)
else:
copytree(src, dst)
def remove(path, recurse=True):
"""Equivalent to rm -f or rm -rf"""
for name in glob.glob(path):
try:
os.unlink(name)
except OSError, exc:
if recurse and exc.errno == errno.EISDIR:
shutil.rmtree(name)
elif exc.errno != errno.ENOENT:
raise
def symlink(source, destination, force=False):
"""Create a symbolic link"""
try:
if force:
remove(destination)
os.symlink(source, destination)
except OSError, e:
if e.errno != errno.EEXIST or os.readlink(destination) != source:
raise
class CalledProcessError(Exception):
def __init__(self, retcode, cmd, output = None):
self.retcode = retcode
self.cmd = cmd
self.output = output
def __str__(self):
return "Command '%s' returned non-zero exit status %d with output %s" % (self.cmd, self.retcode, self.output)
# Not needed when we move to python 2.7
def check_output(*popenargs, **kwargs):
r"""Run command with arguments and return its output as a byte string.
If the exit code was non-zero it raises a CalledProcessError. The
CalledProcessError object will have the return code in the returncode
attribute and output in the output attribute.
The arguments are the same as for the Popen constructor. Example:
>>> check_output(["ls", "-l", "/dev/null"])
'crw-rw-rw- 1 root root 1, 3 Oct 18 2007 /dev/null\n'
The stdout argument is not allowed as it is used internally.
To capture standard error in the result, use stderr=STDOUT.
>>> check_output(["/bin/sh", "-c",
... "ls -l non_existent_file ; exit 0"],
... stderr=STDOUT)
'ls: non_existent_file: No such file or directory\n'
"""
if 'stdout' in kwargs:
raise ValueError('stdout argument not allowed, it will be overridden.')
process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
output, unused_err = process.communicate()
retcode = process.poll()
if retcode:
cmd = kwargs.get("args")
if cmd is None:
cmd = popenargs[0]
raise CalledProcessError(retcode, cmd, output=output)
return output
def find(dir, **walkoptions):
""" Given a directory, recurses into that directory,
returning all files as absolute paths. """
for root, dirs, files in os.walk(dir, **walkoptions):
for file in files:
yield os.path.join(root, file)
## realpath() related functions
def __is_path_below(file, root):
return (file + os.path.sep).startswith(root)
def __realpath_rel(start, rel_path, root, loop_cnt, assume_dir):
"""Calculates real path of symlink 'start' + 'rel_path' below
'root'; no part of 'start' below 'root' must contain symlinks. """
have_dir = True
for d in rel_path.split(os.path.sep):
if not have_dir and not assume_dir:
raise OSError(errno.ENOENT, "no such directory %s" % start)
if d == os.path.pardir: # '..'
if len(start) >= len(root):
# do not follow '..' before root
start = os.path.dirname(start)
else:
# emit warning?
pass
else:
(start, have_dir) = __realpath(os.path.join(start, d),
root, loop_cnt, assume_dir)
assert(__is_path_below(start, root))
return start
def __realpath(file, root, loop_cnt, assume_dir):
while os.path.islink(file) and len(file) >= len(root):
if loop_cnt == 0:
raise OSError(errno.ELOOP, file)
loop_cnt -= 1
target = os.path.normpath(os.readlink(file))
if not os.path.isabs(target):
tdir = os.path.dirname(file)
assert(__is_path_below(tdir, root))
else:
tdir = root
file = __realpath_rel(tdir, target, root, loop_cnt, assume_dir)
try:
is_dir = os.path.isdir(file)
except:
is_dir = false
return (file, is_dir)
def realpath(file, root, use_physdir = True, loop_cnt = 100, assume_dir = False):
""" Returns the canonical path of 'file' with assuming a
toplevel 'root' directory. When 'use_physdir' is set, all
preceding path components of 'file' will be resolved first;
this flag should be set unless it is guaranteed that there is
no symlink in the path. When 'assume_dir' is not set, missing
path components will raise an ENOENT error"""
root = os.path.normpath(root)
file = os.path.normpath(file)
if not root.endswith(os.path.sep):
# letting root end with '/' makes some things easier
root = root + os.path.sep
if not __is_path_below(file, root):
raise OSError(errno.EINVAL, "file '%s' is not below root" % file)
try:
if use_physdir:
file = __realpath_rel(root, file[(len(root) - 1):], root, loop_cnt, assume_dir)
else:
file = __realpath(file, root, loop_cnt, assume_dir)[0]
except OSError, e:
if e.errno == errno.ELOOP:
# make ELOOP more readable; without catching it, there will
# be printed a backtrace with 100s of OSError exceptions
# else
raise OSError(errno.ELOOP,
"too much recursions while resolving '%s'; loop in '%s'" %
(file, e.strerror))
raise
return file